Mushrooms, delicious or deadly?

Yunnan sudden death syndrome occurs in remote mountainous villages of the Yunnan province of China in the rainy season, at an altitude of 1800-2400 m: people just drop dead from heart failure. You might think its linked to the season…some waterborne or insect-carried disease, or maybe the altitude & a genetic quirk, but it turns out that it’s because the villagers make their living collecting & selling wild mushrooms. The only one they can’t sell is a white mushroom, because it’s too small & turns brown quickly after picking. So they eat it…and the Chinese CDC have shown that for a minority of the local population, this mushroom is toxic. Its’ thought that they are sensitive to a combination of the mycotoxins and high barium levels found in the mushroom.(see Rare mushroom blamed for mystery deaths in China)

This reminds me of a passage in a book “The Magic Bullet” (a book about drug development) that I read many years ago, which pointed out that in certain graveyards in the UK, you could find whole families who died together in medieval times, and not through the plague. These deaths were linked to poor harvests. It turned out these families’ had been forced to turn to foraging for mushrooms (an action we now term using “famine food”), and even though villagers in general were probably more expert than we are now at identifying safe ones, one mistake added to the family pot, and that was that!

But don’t be complacent: in the UK in 2009 the case of two Thai women hit national headlines. One of them misidentified an English mushroom and the result was that she cooked and ate a number of them, and died.  The other who ate fewer of them became seriously ill with liver failure. It was a death-cap mushroom… just half of one of these is sufficient to kill an adult. (see Isle of Wight woman died… )

I decided to see what records our Global Health database has on toxic mushrooms & other fungi, their toxins (mycotoxins) and cases of human poisoning by them.

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Can Bt Maize Beat Down Mycotoxins?

Bt maize (which contains a toxin gene from Bacillus thuringiensis) is genetically engineered to limit damage from certain insect pests. Fungal infestation, which leads to mycotoxin contamination, is known to follow pest damage. So can the Bt toxin also help by reducing mycotoxins in maize?

Felicia Wu from the University of Pittsburgh examines the sometimes conflicting evidence in a paper in CAB Reviews. Aflatoxin is the most serious mycotoxin in terms of financial impact, and it appears that levels of this toxin are not consistently reduced in Bt maize in comparison to non-Bt maize, although future Bt maize varieties may have a more positive effect. However, fumonisin, another important mycotoxin, is reduced in almost all studies. Fumonisin is associated with oesophageal cancer and neural tube defects. Reducing fumonisin through Bt could have significant benefits in developing countries, especially where unprocessed maize is a key part of the diet, and so mycotoxins are present at levels which can health problems. It also could help them avoid losses in the export market through rejection of contaminated maize.

The paper, “Bt corn and impact on mycotoxins” appears in CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources, 2007, 2, No. 060, 8 pp.